Investments in early decision-making about sexual risk-taking often have lifetime benefits and may be especially important for youth of minority groups. American Indian (AI) youth have almost twice the rate of chlamydia found in the national population, even at the youngest ages (10-14), and represent 21% of all AI AIDS cases. The low but rising numbers of AIDS/HIV cases in combination with high rates of STDs support the pressing need for effective prevention in these communities. Meaningful evaluation of HIV/STD prevention efforts aimed at youth, however, is often absent, and the results of those with rigorous designs have been ambiguous. In part, the uncertain findings may be explained by the lack of integration of theoretical frameworks into the analyses of intervention effectiveness: Few have accounted for predisposing factors or developmental trajectories that may diminish the effects of an intervention. In short, youth are likely to respond differently to the same intervention. This project will assess the impact of an HIV prevention intervention curriculum designed explicitly for AI middle-school youth in partnership with 15 middle schools in an AI community. Using Social Cognitive Theory as a framework, we can also account for social context and prior developmental trajectories. Such contextualized interpretation of results is likely to be particularly important in AI reservation communities, many of which endure high levels of morbidity, trauma, and poverty, even while family and cultural life are strong. Furthermore, most prevention programs for youth have focused on urban youth. We know little about how culturally appropriate interventions might work with AI youth in rural settings. The project has four aims: [1] To assess the impact of the intervention on sexual-risk knowledge, expectancies, and behaviors (KEBs) among a sample of AI youth; [2] to determine the impact of the intervention on developmental trajectories of sexual risk and KEBs in this sample of youth, and the effect of varying exposure levels of the intervention on those trajectories; [3] to develop theoretically salient groupings of youth based on initial risk status, family and community context, and risk patterns over time, and to determine the extent to which the impact of the intervention varies by group; and [4] to develop a "best practices" model of sexual risk intervention for AI youth in consultative feedback sessions with educators, community members, and youth. [unreadable] [unreadable]